This invention relates to resid hydrotreating and, more particularly, to an improved hydrotreating process and novel ebullated bed reactor equipped with a unique floating pan.
In the past, spiraling oil costs, extensive price fluctuations, and artificial output limitations by the cartel of oil producing countries (OPEC) have created instability and uncertainty for net oil consuming countries, such as the United States, to attain adequate supplies of high-quality, low-sulfur, petroleum crude oil (sweet crude) from Saudi Arabia, Nigeria, Norway, and other countries at reasonable prices for conversion into gasoline, fuel oil, and petrochemical feedstocks. In an effort to stabilize the supply and availability of crude oil at reasonable prices, Amoco Oil Company has developed, constructed, and commercialized extensive refinery projects to process poorer quality, high-sulfur, petroleum crude oil (sour crude) and demetalate, desulfurize, and hydrocrack resid to produce high-value products, such as gasoline, distillates, catalytic cracker feed, metallurgical coke, and petrochemical feedstocks. Thus, it is to our country's benefit to provide for the availability of adequate supplies of gasoline and other petroleum products at reasonable prices.
During resid hydrotreating, resid oil (resid) is upgraded with hydrogen and a hydrotreating catalyst in a three-phase equilibrium of oil, catalyst, and gas bubbles to produce more valuable, lower-boiling liquid products. In order to increase the efficiency, effectiveness, and profitability of resid hydrotreating, it is desirable to maximize the conversion of resid to more valuable lower-boiling liquid products.
The extent of conversion of resid to more valuable lower-boiling liquid products depends in part on the residence time of the resid in the reactor.
During resid hydrotreating in ebullated bed reactors, an oil feed comprising oil and hydrogen-rich gases and fresh hydrotreating catalysts are fed and circulated in a vessel. In prior art devices, a stationary tubular downcomer with a stationary (fixed) pan extends upwardly above an ebullating pump. The ebullating pump circulates the feed upwardly in the reaction zone of the vessel, expanding the catalyst bed. The liquid level therein fluctuates above and below the stationary pan and downcomer. When the liquid level dips below the top of the stationary pan, the oil feed does not circulate through the pan, downcomer, risers, bubble caps, and the reaction zone which can cause the liquid to become stagnant and hot spots to build up in the reactor which can be dangerous. Loss of liquid circulation can cause equipment and/or catalyst damage, require shutdown of the hydrotreating unit, and/or upset downstream equipment.
It is, therefore, desirable to provide an improved hydrotreating process and reactor for increasing the conversion of resid which overcomes most, if not all, of the above problems.